Subject: [patch V3 10/12] futex: Convert to scoped masked user access

From: Thomas Gleixner <[email-masked]>
Date: Fri, 17 Oct 2025 12:09:14 +0200 (CEST)

From: Thomas Gleixner <[email-masked]>

Replace the open coded implementation with the new get/put_user_masked()
helpers.

No functional change intended

Signed-off-by: Thomas Gleixner <[email-masked]>
Cc: Peter Zijlstra <[email-masked]>
Cc: Darren Hart <[email-masked]>
Cc: Davidlohr Bueso <[email-masked]>
Cc: "André Almeida" <[email-masked]>
---
V3: Adapt to scope changes
V2: Convert to scoped variant
---
 kernel/futex/futex.h |   37 ++-----------------------------------
 1 file changed, 2 insertions(+), 35 deletions(-)
---
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -285,48 +285,15 @@ static inline int futex_cmpxchg_value_lo
  * This does a plain atomic user space read, and the user pointer has
  * already been verified earlier by get_futex_key() to be both aligned
  * and actually in user space, just like futex_atomic_cmpxchg_inatomic().
- *
- * We still want to avoid any speculation, and while __get_user() is
- * the traditional model for this, it's actually slower than doing
- * this manually these days.
- *
- * We could just have a per-architecture special function for it,
- * the same way we do futex_atomic_cmpxchg_inatomic(), but rather
- * than force everybody to do that, write it out long-hand using
- * the low-level user-access infrastructure.
- *
- * This looks a bit overkill, but generally just results in a couple
- * of instructions.
  */
 static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
 {
-	u32 val;
-
-	if (can_do_masked_user_access())
-		from = masked_user_access_begin(from);
-	else if (!user_read_access_begin(from, sizeof(*from)))
-		return -EFAULT;
-	unsafe_get_user(val, from, Efault);
-	user_read_access_end();
-	*dest = val;
-	return 0;
-Efault:
-	user_read_access_end();
-	return -EFAULT;
+	return get_user_masked(*dest, from) ? 0 : -EFAULT;
 }
 
 static __always_inline int futex_put_value(u32 val, u32 __user *to)
 {
-	if (can_do_masked_user_access())
-		to = masked_user_access_begin(to);
-	else if (!user_write_access_begin(to, sizeof(*to)))
-		return -EFAULT;
-	unsafe_put_user(val, to, Efault);
-	user_write_access_end();
-	return 0;
-Efault:
-	user_write_access_end();
-	return -EFAULT;
+	return put_user_masked(val, to) ? 0 : -EFAULT;
 }
 
 static inline int futex_get_value_locked(u32 *dest, u32 __user *from)